Numerical Modelling of AC Hysteresis Losses in HTS Tubes

AC losses in superconducting cables are generated by a time varying environment. These losses heat the cable and impact the cooling system. Nexans is today on the edge of manufacturing superconducting tubes with HTS tapes to create compact high power cables. No study has been done yet on the numerical modelling of ac losses for this new geometry. This article presents the recent development of the creation of a finite-element model (FEM) model to estimate the ac hysteresis losses in a tube. The E-J nonlinearity and convergence issues were solved with the use of a H-formulation. Several E-J formulations have also been compared. To validate the model, an experiment has been performed with a superconducting commercial tape with different waveform of current at different amplitudes and frequencies. Numerical results have been compared to analytical calculations with self-field and external magnetic field losses. In a power cable, HTS tubes are exposed to both a transport current and external magnetic field. The behavior of the tube under both a time varying current and external magnetic field has been studied. Finally some geometries of small cables made of 3 or 6 tubes have been modeled.